1. Field of the Invention
The present invention relates to testing of integrated circuits, and more specifically to a method and apparatus for testing mixed signal integrated circuits which generate analog signals from digital data elements.
2. Related Art
Mixed signal integrated circuits (IC) generally refer to circuits which operate on both analog and digital signals. Mixed signal ICs are used in several areas such as communications (both wireless and wire-based) in which digital data elements are converted into analog signals which are eventually transmitted.
A receiving system (using another mixed signal IC) recovers the digital data elements from the analog signals. Other digital data elements may then be transferred in the reverse direction as well. The data thus exchanged is used to support several user applications (e.g., voice calls, networking), as is well known in the relevant arts.
Testing is often performed to determine whether an integrated circuit operates according to design specifications. It may be necessary to discard at least integrated circuits which substantially deviate from the design specification. Thus, by performing such testing, one may ensure that only end products which provide an intended utility, are supplied/sold in the market place.
It is often desirable to test an IC before the IC is integrated into end products, which are eventually sold/supplied. As an illustration, an IC may be placed in a package, the packaged IC may then be placed on a board, and the board may be eventually used in a system which is sold/supplied to an end customer. By testing and discarding the IC at an early stage (e.g., before being placed in a package), unneeded wastage of resources (cost/time/effort) may be avoided.
In one prior testing approach, a transceiver (containing a transmitter, receiver and an antenna) is placed in a loop-back mode in which the output of the transmitter is connected to the input of the receiver, bypassing the antenna. The transmitter converts a sequence of digital data elements into analog signals, which are received by the receiver. The receiver generates a sequence of digital data elements from the received analog signal. Deviations from the design specifications may be determined based on the signal strength of the received analog signals, comparison of the digital data elements used in the transmitter and receiver, etc.
Thus, the prior approach of above enables testing of a transceiver, potentially when the corresponding IC is not yet packaged (and thus only as a stand-alone wafer). one problem with the approach is that many transceivers use common components in the transmit and receive paths, and simultaneous use of both the paths may not thus be possible. In addition, loop-back approaches often skip some portions/stages of the transmit/receive paths, and the test results may accordingly not be reliable.
What is therefore needed is an improved method and apparatus for testing of mixed signal integrated circuits generating analog signals from digital data elements.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.